CMOS transducer with linear response using negative capacity that can be used in mechatronic systems for force measurement in human walking analysis and in the future in MEMS and NEMS applications

Abstract

The paper describes a methodology to linearize the signals obtained from capacitive force sensors. The approach is based on the theoretical analysis of a negative capacitance circuit adjusted to compensate to the parasitic capacitances that are formed in parallel with the sensor. I describe an original method of linearization using a negative capacitance calculated based on the Laplace Analysis of the one auxiliary circuit added to the main oscillator. This auxiliary circuit, called “Neutrodyne” is a neutralization circuit and provides a negative capacitance that compensates the parasitic one. The result is a rectangular signal with linear frequency dependent on the force or pressure applied. This linearization method can be used in a variety of other applications: mechatronic systems, gait analysis, microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). In our project, the transducer is used for measuring the calibrated Ground Reaction Force during gait in order to calculate the total caloric consumption of the body for horizontal components of forces application points.